--- title: "Anodizing Coating Thickness Calculator" description: >- Free anodizing coating thickness calculator. Compute oxide layer in microns from current density (A/dm²) and time. Type II sulphuric and Type III hard. canonical: "https://www.saravanaconsultancy.in/calculators/coating-thickness" source_url: html: "https://www.saravanaconsultancy.in/calculators/coating-thickness" md: "https://www.saravanaconsultancy.in/calculators/coating-thickness.md" last_modified: 2026-05-24 --- Free Calculator # Anodizing Coating Thickness Calculator Compute the anodic oxide layer in microns from current density and time. Switch between Type II sulphuric and Type III hard anodizing presets, or back-solve the time you need to hit a target thickness. ## Inputs Solve for thickness Solve for time Process type Type II — sulphuric anodizing (18% H₂SO₄, 20 °C) Type III — hard anodizing (15% H₂SO₄, 0 °C) Custom K factor Current density (A/dm²) Type II: 1.2-1.8 typical · Type III: 2.5-3.6 typical Process time (minutes) Target thickness (microns) Bath efficiency (0.5 - 1.0) 0.80 = healthy bath · 0.65 = struggling bath · 1.00 = theoretical max K factor (µm per A/dm²-min, 100% efficiency) ## Result Predicted oxide thickness 12.0 µm Build-up rate 0.30 µm/min Charge passed 60 A·min/dm² Time to hit target — min ## How this works Anodic oxide growth follows Faraday's law of electrolysis. For practical plant use, the industry simplifies it to: thickness (µm) = K × current density (A/dm²) × time (min) × efficiency ### What K means - **K = 0.30** — Type II sulphuric anodizing at 18-22 °C in 180-200 g/L H₂SO₄. Standard architectural and decorative anodizing. - **K = 0.50** — Type III hard anodizing at -2 to 2 °C in 150 g/L H₂SO₄. Wear-resistant engineering coatings. - **K = 0.40** — Mixed-acid or oxalic processes (use the custom mode). ### Why efficiency matters Theoretical Faraday yield is never reached because some oxide re-dissolves into the acid bath, and some current is lost to side reactions and ohmic heating. A well-controlled Type II bath runs at 80-85% efficiency. If you are seeing under-thickness on parts that should be in spec, dropping efficiency to 0.65 in the calculator usually matches what is happening in your tank. ### Common quick-reference values - Type II at 1.5 A/dm², 80% efficiency → ~0.36 µm/min → 25 µm in 70 min - Type II at 1.8 A/dm², 80% efficiency → ~0.43 µm/min → 25 µm in 58 min - Type III at 3.0 A/dm², 80% efficiency → ~1.20 µm/min → 50 µm in 42 min ### Numbers don't match your line? If your bath is consistently producing under-spec coatings even at the right current density and time, the problem is usually in the bath chemistry, temperature control, or rectifier ripple. We can diagnose it on a single plant visit. [Get a plant audit](/contact) ## Frequently asked questions How is anodizing thickness calculated? Anodic oxide thickness in microns is approximated as K × current density (A/dm²) × time (min) × efficiency, where K ≈ 0.30 for Type II sulphuric anodizing at 20 °C and K ≈ 0.50 for Type III hard anodizing at 0 °C. Practical efficiency is usually 70-85% due to ohmic losses and re-dissolution of oxide in the acid bath. What is a typical current density for Type II anodizing? Type II sulphuric anodizing typically runs at 1.2-1.8 A/dm² in 18% sulphuric acid at 18-22 °C, producing roughly 1 micron per minute at the upper end of that range with bath efficiency around 80%. What current density is used for hard anodizing? Type III hard anodizing typically runs at 2.5-3.6 A/dm² in 15% sulphuric acid chilled to -2 to 2 °C, producing 25-50 micron coatings in 30-60 minutes. Higher current density requires aggressive bath cooling to prevent burning. Why does my actual thickness fall short of the calculated value? Three common causes: bath temperature too high (re-dissolves oxide), aluminium alloy with high copper or silicon (lower CE), and poor electrical contact at the jig (current shadow). Drop calculator efficiency to 0.65 to model a struggling bath. What does MIL-A-8625 specify for thickness? MIL-A-8625 Type II Class 1 (clear) requires minimum 1.8 micron; Class 2 (dyed) requires 7-25 micron typical. Type III Class 1 requires 50 micron nominal; Class 2 requires 25-50 micron dyed. Use this calculator to back-solve the time you need at your chosen current density. See our [MIL-A-8625 anodising guide](/blog/mil-a-8625-anodising-india) for full classification details. Related: [Anodizing plant cost calculator](/calculators/anodizing-plant-cost) · [Bath chemistry reference](/blog/anodising-bath-chemistry-reference-india) · [Type II vs Type III comparison](/blog/hard-anodizing-vs-sulphuric-anodizing)